Vector / ArrayList - Size increment

ArrayList and Vector are internally implemented with Object[] with dynamically expands as we add more objects. But its interesting to know why people stress on using arrays if at all possible in the place these utilities.

These dynamic arrays increases the memory in folds.

ArrayList - default capacity 10

int newCapacity = (oldCapacity * 3)/2 + 1;


Vecor - default capacity

int newCapacity = (capacityIncrement > 0) ?
(oldCapacity + capacityIncrement) : (oldCapacity * 2);



So its better to initialize these objects with proper initial capacity to avoid performance issues.